Reducing global NOx emissions: developing advanced energy and transportation technologies

Globally, energy demand is projected to continue to increase well into the future. As a result, global NOx emissions are projected to continue on an upward trend for the foreseeable future as developing countries increase their standards of living. While the US has experienced improvements in reducing NOx emissions from stationary and mobile sources to reduce ozone, further progress is needed to reduce the health and ecosystem impacts associated with NOx emissions. In other parts of the world, (in developing countries in particular) NOx emissions have been increasing steadily with the growth in demand for electricity and transportation. Advancements in energy and transportation technologies may help avoid this increase in emissions if appropriate policies are implemented. This paper evaluates commercially available power generation and transportation technologies that produce fewer NOx emissions than conventional technologies, and advanced technologies that are on the 10-year commercialization horizon. Various policy approaches will be evaluated which can be implemented on the regional, national and international levels to promote these advanced technologies and ultimately reduce NOx emissions. The concept of the technology leap is offered as a possibility for the developing world to avoid the projected increases in NOx emissions.     

Characterization and phosphate stabilization of dusts from the vitrification of MSW combustion residues

The use of soluble PO₄³⁻ as a heavy metal chemical stabilization agent was evaluated for a dust generated from melting or vitrification of municipal solid waste combustion residues. Vitrification dusts contain high concentrations of volatile elements such as Cl, Na, K, S, Pb, and Zn. These elements are present in the dusts largely as simple salts (e.g. PbCl₂, ZnSO₄) which are highly leachable. At an experimental dose of 0.4 moles of soluble PO₄³⁻ per kg of residue, the pH-dependent leaching (pH 5,7,9) showed that the treatment was able to reduce equilibrium concentrations by factors of 3 to 100 for many metals; particularly Cd, Cu, Pb and Zn. Bulk and surface spectroscopies showed that the insoluble reaction products are tertiary metal phosphate [e.g. Zn₃(PO₄)₂] and apatite [e.g. Pb₅(PO₄)₃Cl] family minerals. Geochemical thermodynamic equilibrium modeling showed that apatite family and tertiary metal phosphate phases act as controlling solids for the equilibrium concentrations of Ca²⁺, Zn²⁺, Pb²⁺, Cu²⁺, and Cd²⁺ in the leachates during pH-dependent leaching. Both end members and ideal solid solutions were seen to be controlling solids. Soluble phosphate effectively converted soluble metal salts into insoluble metal phosphate phases despite the relatively low doses and dry mixing conditions that were used. Soluble phosphate is an effective stabilization agent for divalent heavy metals in melting dusts where leachable metals are present in high concentrations.     

Invasion dynamics of the varnish clam (Nuttallia obscurata): a matrix demographic modeling approach

Marine invaders have become a significant threat to native biodiversity and ecosystem function. In this study, the invasion of the varnish clam (Nuttallia obscurata) in British Columbia, Canada, is investigated using a matrix modeling approach to identify the life history characteristics most crucial for population growth and to investigate population differences. Mark-recapture analyses and field collections from 2003 to 2004 were used to determine individual growth, survival rates, and fecundity for two sites. A multi-state matrix model was used to determine population growth rates and to conduct sensitivity and elasticity analyses. A life table response experiment was also used to determine what life history stage contributed most to observed differences in population growth rates. Population survey data were used in conjunction with the matrix model to determine plausible recruitment levels and to investigate recruitment scenarios. Both populations are currently declining but are likely sustainable because of the pulsed nature of large recruitment events. Survival of larger clams (>40 mm) is the most important for population growth based on elasticity and sensitivity analyses. Adult survival also had the largest influence on observed differences between site-specific population growth rates. The two populations studied differed in recruitment dynamics; one experiencing annual recruitment with higher post-settlement mortality and the other, episodic recruitment and lower post-settlement mortality. The most influential factor for the successful invasion of the varnish clam appears to be survival of the larger size classes. Therefore, any process that decreases adult survival (e.g., predation, commercial harvest) will have the greatest impact on population growth.     

Mortality rate and confidence interval estimation in humanitarian emergencies

Surveys are conducted frequently in humanitarian emergencies to assess the health status of the population. Most often, they employ complex sample designs, such as cluster sampling. Mortality is an indicator commonly estimated in such surveys. Confidence limits provide information on the precision of the estimate and it is important to ensure that confidence limits for a mortality rate account for the survey design and utilise an acceptable methodology. This paper describes the calculation of confidence limits for mortality rates from surveys using complex sampling designs and a variety of software programmes and methods. It contains an example that makes use of the SAS, SPSS, and Epi Info software programmes. Of the three confidence interval methods examined—the ratio command approach, the modified rate approach, and the modified proportion approach—the paper recommends the ratio command approach to estimate mortality rates with confidence limits.     

BIODEGRADATION OF DISINFECTION BYPRODUCTS AS A POTENTIAL REMOVAL PROCESS DURING AQUIFER STORAGE RECOVERY1

ABSTRACT: The biodegradation potential of two drinking water disinfection byproducts was investigated using aquifer materials obtained from approximately 100 and 200 meters below land surface in an aerobic aquifer system undergoing aquifer storage recovery of treated surface water. No significant biodegradation of a model trihalomethane compound, chloroform, was observed in aquifer microcosms under aerobic or anaerobic conditions. In contrast, between 16 and 27 percent mineralization of a radiolabeled model haloacetic acid compound, chloroacetic acid, was observed. These results indicate that although the potential for biodegradation of chloroacetic acid exists in deep aquifer systems, chloroform entrained within these aquifers or formed in situ will tend to persist. These results have important implications for water managers planning to meet anticipated lowered permissible levels of trihalomethanes in drinking water.     

Relationships between analytical methods utilized as tools in the evaluation of landfill waste stability

In this study, the refuse from 12 landfills of various ages ranging from fresh refuse to material 11 years old was collected, and changes in the bio-stability parameters were determined. The parameters measured included cellulose, lignin, biochemical methane potential (BMP) and volatile solids, along with plastics. These parameters, along with the cellulose to lignin ratio were compared to determine which were most indicative of the bio-stability of the refuse. Lignin and volatile solids measurements were affected by plastics in refuse samples. Plastics increased both lignin and volatile solids measurements by approximately 10%. Cellulose and volatile solids measurements correlated well with age, each other, and with BMP measurements and were therefore considered the best parameters to determine stability. Data for the Riverbend landfill, a landfill with a moisture content of 48%, which is similar to that of bioreactor landfills, showed that degradation was nearly complete after 5 years as indicated by low values for cellulose and BMP.     

Nuclear magnetic resonance logging: Example applications of an emerging tool for environmental investigations

Nuclear magnetic resonance (NMR) geophysical tools have been widely used in the petroleum exploration industry since the 1960s and have improved significantly in the last two decades. These tools can provide estimates of bulk porosity and fluid content, quantification of bound versus mobile fluids, and estimates of hydraulic conductivity (K). Although the size and cost of oil‐field tools historically limited their use for near‐surface applications, smaller and more economical downhole NMR logging tools are now available for detecting and characterizing the formation water content and K to support environmental and groundwater resource investigations. These tools can be deployed using direct‐push drilling techniques or they can be lowered into existing open borings or wells with nonconductive polyvinyl chloride casings and screens. In many cases, using the tool in existing wells offers a safer and more cost‐effective alternative compared to drilling new boreholes. For environmental investigations, NMR can provide useful high‐resolution quantitative hydrostratigraphic information that can provide additional valuable data to further inform and refine the conceptual site model. This paper highlights several NMR field investigations that demonstrate the viability of this technology as a site characterization tool for near‐surface investigations. NMR measurements were compared to data from lithologic logs, cone penetrometer testing data, and prior field hydraulic tests. Use of NMR to detect vadose zone water, including previously unidentified perched groundwater zones, provided hydrostratigraphic details that could not be gleaned from historical well drilling logs and were used to evaluate drainable pore water versus pore water bound in small pores by capillary forces or electrochemically clay‐bond water. NMR also produced K estimates similar to those from conventional hydraulic tests, but the improved vertical resolution from NMR provided additional information regarding the vertical heterogeneity of the formation along the entire length of the well or borehole. Additionally, bench‐scale tests are presented that confirm the capability for NMR to reliably detect and quantify light nonaqueous phase liquid saturation (specifically diesel fuel and weathered gasoline) in situ. The field tests combined with bench‐scale testing results affirm the applicability and potential for NMR as a practical characterization tool that should increasingly be utilized in environmental investigations.     

Occurrence and behavior of per‐ and polyfluoroalkyl substances from aqueous film‐forming foam in groundwater systems

Per‐ and polyfluoroalkyl substances (PFAS) are fluorinated compounds and the active ingredient in aqueous film‐forming foam (AFFF). AFFF has been identified as a significant source of PFAS contamination in groundwater. PFAS are also present in many other industrial and consumer products and their manufacture and use has led to numerous contaminated sites. Human health risks have been identified with studies linking firefighter cancers to training facilities where AFFF was used. Given the widespread release of these compounds to the environment and their potential health risks, understanding their mobility characteristics is important. This article details the occurrence and behavior of these substances in groundwater systems to help guide the emerging fields of PFAS investigation and remediation. Background is presented on AFFF and PFAS source characteristics, including common industrial and consumer PFAS sources. In addition, chemical properties, sorption and retention parameters, and observed transformation properties of PFAS and related compounds are discussed. Finally, knowledge gaps are identified for future laboratory and field studies.